Your car is watching you: Event Data Recorders explained

We’re used to cars storing information to diagnose faults, but should we be concerned about a little-known crash data detection system?

Data is big business nowadays and even the briefest of internet searches will reveal all manner of lively discussion about the information that your car is collecting. It’s become especially relevant in the era of infotainment systems and connected services, but there’s another piece of technology that you might not be aware of: the Event Data Recorder, or EDR.
They have been installed in pretty much all cars for more than a decade, originally intended to simply help car makers understand how their vehicle behaved in a crash (such as how quickly airbags had deployed). Although, accessing the information they contained wasn’t always straightforward. 
We’ll come back to that later, but firstly: where is the EDR and what does it do? The first question is easy to answer, because the EDR electronics are contained within the airbag control module (also known as the restraint control module). This is the unit that decides that some sort of collision is about to take place and triggers safety items, such as airbags and seatbelt pretensioners. 
As for what the EDR does, it’s actually relatively straightforward. Essentially, it gathers data from a wide range of sensors that monitor parameters, such as wheel speed, throttle inputs, brake application, steering angle and whether seatbelts are in use. More than a dozen parameters can be measured, all of which provide an accurate picture of the car at any given moment, matched to both date and time. 
However, it isn’t recording such data on a continual basis. Although always ready to do so, recording only happens when the safety system’s electronic brain thinks something bad could be about to occur. It’s possible it might be triggered by something minor, such as a very small bump, or the shock of hitting a large pothole, but it means airbags and the like are primed and ready should things escalate. 
At this point, the EDR will start recording the data it’s being fed from the various inputs. If it turns out to be a false alarm, and no crash happens, the airbag module will mark it as a “non-deployment” event – so airbags are not triggered – and the EDR data will most likely be overwritten (although in some cases it may remain in the system for a while). If a crash ensues, the measurements are saved. What’s saved is five seconds of data before the actual crash, as well as data recorded during the impact itself, which cannot be overwritten. 
This is where things get interesting.
Returning to accessing the resulting crash data, that was a bit of a problem because at first it was something only the car’s manufacturer could do. Although access for other agencies had been mandatory in the US, this wasn’t the case in Europe – although that’s expected to change after a United Nations (UN) Regulation mandating speed limiters came into force in July. 
But things really shifted when automotive giant Bosch launched its “Crash Data Retrieval” tool – it was a gamechanger for the world of collision investigation. For experts like those at the UK’s Transport Research Laboratory (TRL), it meant that piecing together what had happened became far easier.
Craig Arnold is the Technical Lead in forensic collision investigations at TRL. He told me that the use of EDR data has really grown in recent years. Although he is understandably reluctant to discuss actual figures, he confirms that it gets used in a large number of cases TRL investigates. But he stresses that having the data is only part of the story. 
“You still need expert analysis to understand exactly what the data is telling you, especially in cases where there might have been multiple impacts. For example, when a vehicle strikes a number of other vehicles or roadside items before coming to rest – which then provides us with a number of individual sections of data,” he says. 
“Determining exactly what happened and in what order can be complex.”
It’s certainly easy to see how data such as this can be incredibly useful in establishing a driver’s actions prior to a collision, especially where other evidence, such as CCTV, might not provide a clear picture of events. For example, information from an EDR can show whether a driver applied the brakes or not before impact. Additionally, this information can help establish whether an incident was the result of driver error or a vehicle defect – such as a case of “unintended acceleration,” where the data will show which pedals were being pressed and how hard. 
In 2012, an EDR was used for the first time in the UK during investigations into a fatal car crash – with the technology able to prove that a car was speeding. 
Investigators can usually download EDR information by plugging the retrieval tool into the car’s on-board diagnostics socket. Although, should a collision be serious enough to have caused failure of the car’s electrical system, it may be necessary to remove the airbag module for a direct download. However, such a power failure could have prevented anything being recorded, so the system isn’t foolproof. 
Yet the apparent ease with which EDR data can be accessed might raise a few privacy concerns with owners, so is it something we should be worried about? Not according to Arnold, who points out that the data is really only of use to vehicle engineers and investigators like him. Additionally, the retrieval tool is expensive, so it’s not something the average owner would invest in. In any case, should a car never experience an event that primes the safety systems, the EDR’s memory will remain blank. To add further peace of mind, the data can only be recovered with physical access to the car, not remotely. That should negate any “Big Brother” fears you might be having. 
Ultimately, this system should be viewed as a very important tool that might help to prove your innocence should the worst happen. Or your guilt, of course…